U.S. patent application number 16/474333 was filed with the patent office on 2019-11-21 for travel path recognition apparatus and travel path recognition method.
This patent application is currently assigned to Mitsubishi Electric Corporation. The applicant listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Yasuyoshi HORI.
Application Number | 20190351901 16/474333 |
Document ID | / |
Family ID | 60989173 |
Filed Date | 2019-11-21 |
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United States Patent
Application |
20190351901 |
Kind Code |
A1 |
HORI; Yasuyoshi |
November 21, 2019 |
TRAVEL PATH RECOGNITION APPARATUS AND TRAVEL PATH RECOGNITION
METHOD
Abstract
An object is to provide technology capable of appropriately
recognizing a travel path. A travel path recognition apparatus
includes a travel path recognizer. The travel path recognizer
calculates a traveling distance traveled by a vehicle from
acquisition time of lane marking information to current time based
on a vehicle speed of vehicle behavior. Then, the travel path
recognizer determines whether or not the lane marking information
is information within a usable period in which the lane marking
information is usable to recognize the travel path based on a
predetermined lane marking acquirable distance and the traveling
distance. The predetermined lane marking acquirable distance is a
distance in front of a position of the vehicle, and is a distance
in which a lane marking of the lane marking information is
acquirable.
Inventors: |
HORI; Yasuyoshi; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
Mitsubishi Electric
Corporation
Tokyo
JP
|
Family ID: |
60989173 |
Appl. No.: |
16/474333 |
Filed: |
January 10, 2017 |
PCT Filed: |
January 10, 2017 |
PCT NO: |
PCT/JP2017/000405 |
371 Date: |
June 27, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60W 2552/53 20200201;
G06T 7/60 20130101; B60W 2552/30 20200201; B60W 40/04 20130101;
G01C 21/14 20130101; B60W 30/12 20130101; G06K 9/00798 20130101;
B60W 2420/42 20130101; G08G 1/16 20130101; B60W 40/06 20130101 |
International
Class: |
B60W 30/12 20060101
B60W030/12; G01C 21/14 20060101 G01C021/14; G06K 9/00 20060101
G06K009/00 |
Claims
1. A travel path recognition apparatus comprising: a lane marking
receiver configured to acquire lane marking information concerning
a position and a shape of a lane marking in front of a vehicle with
respect to a position of the vehicle; a vehicle behavior receiver
configured to acquire vehicle behavior concerning a vehicle speed
of the vehicle from acquisition time of the lane marking
information to current time; and a travel path recognizer
configured to recognize a travel path on which the vehicle travels
based on the lane marking information, wherein the travel path
recognizer calculates a traveling distance traveled by the vehicle
from the acquisition time of the lane marking information to the
current time based on the vehicle speed of the vehicle behavior,
and determines whether or not the lane marking information is
information within a usable period in which the lane marking
information is usable to recognize the travel path based on a
predetermined lane marking acquirable distance and the traveling
distance, the predetermined lane marking acquirable distance being
a distance in front of the position of the vehicle, and being a
distance in which the lane marking of the lane marking information
is acquirable.
2. The travel path recognition apparatus according to claim 1,
further comprising an inter-vehicle distance receiver configured to
acquire an inter-vehicle distance between a preceding vehicle and
the vehicle, the preceding vehicle being another vehicle in front
of the vehicle, wherein the travel path recognizer controls the
lane marking acquirable distance based on the inter-vehicle
distance.
3. The travel path recognition apparatus according to claim 1,
wherein the lane marking information includes curvature of the lane
marking, and the travel path recognizer controls the lane marking
acquirable distance based on the curvature.
4. The travel path recognition apparatus according to claim 1,
wherein the lane marking information includes curvature of the lane
marking, and a vehicle angle, the vehicle angle being inclination
of a traveling direction of the vehicle with respect to a portion
of the lane marking on a side of the vehicle, and the travel path
recognizer controls the lane marking acquirable distance based on
the curvature and the vehicle angle.
5. The travel path recognition apparatus according to claim 1,
wherein the vehicle behavior includes behavior concerning a yaw
rate of the vehicle from the acquisition time of the lane marking
information to the current time, and the travel path recognizer
corrects the lane marking information within the usable period into
current-position lane marking information based on the vehicle
behavior, and uses the current-position lane marking information to
recognize the travel path, the current-position lane marking
information concerning the position and the shape of the lane
marking with respect to a current position of the vehicle.
6. A travel path recognition method comprising: acquiring lane
marking information concerning a position and a shape of a lane
marking in front of a vehicle with respect to a position of the
vehicle; acquiring vehicle behavior concerning a vehicle speed of
the vehicle from acquisition time of the lane marking information
to current time; and recognizing a travel path on which the vehicle
travels based on the lane marking information, wherein the
recognizing of the travel path includes calculating a traveling
distance traveled by the vehicle from the acquisition time of the
lane marking information to the current time based on the vehicle
speed of the vehicle behavior, and determining whether or not the
lane marking information is information within a usable period in
which the lane marking information is usable to recognize the
travel path based on a predetermined lane marking acquirable
distance and the traveling distance, the predetermined lane marking
acquirable distance being a distance in front of the position of
the vehicle, and being a distance in which the lane marking of the
lane marking information is acquirable.
Description
TECHNICAL FIELD
[0001] The present invention relates to a travel path recognition
apparatus and a travel path recognition method that recognize a
travel path on which a vehicle travels.
BACKGROUND ART
[0002] A Vehicle including a lane keep assist function uses a
travel path recognition apparatus that recognizes a travel path on
which the vehicle travels. For example, a travel path recognition
apparatus disclosed in Patent Document 1 estimates a traffic lane
border based on a sequence of points of traffic-lane candidate
points corresponding to a detected traffic lane border, and sets a
prediction parameter coefficient after traveling for a set time
period based on a sequence of points before traveling for a set
time period with respect to calculation time of the current case.
Then, the travel path recognition apparatus estimates a traffic
lane after traveling for the set time period based on this
prediction parameter coefficient. Specifically, according to the
travel path recognition apparatus disclosed in Patent Document 1, a
prediction parameter coefficient after traveling for a set time
period is set based on a sequence of points of previous
traffic-lane candidate points, and a traffic lane is estimated
based on this prediction parameter coefficient.
PRIOR ART DOCUMENT
Patent Document
[0003] Patent Document 1: Japanese Patent Application Laid-Open No.
2012-058984
SUMMARY
Problem to be Solved by the Invention
[0004] In the technology described in Patent Document 1 above, if a
traffic lane recognition distance cannot be sufficiently secured
and a lane marking cannot be detected, such as in a case where a
distant view of a driver of a vehicle following a preceding vehicle
is blocked by the preceding vehicle, old parameters are used to
estimate the lane marking for securing safety. However, Patent
Document 1 does not define a usable period of each parameter, or
does not especially make a reference to a usable period in which
information of a detected traffic lane can be used. Therefore,
there is a problem in that the travel path on which the vehicle
travels cannot be appropriately recognized.
[0005] Accordingly, the present invention has been achieved in view
of the problems as described above, and has an object to provide
technology capable of appropriately recognizing a travel path.
Means to Solve the Problem
[0006] According to the present invention, a travel path
recognition apparatus includes a lane marking acquisition unit
configured to acquire lane marking information concerning a
position and a shape of a lane marking in front of a vehicle with
respect to a position of the vehicle, a vehicle behavior
acquisition unit configured to acquire vehicle behavior concerning
a vehicle speed of the vehicle from acquisition time of the lane
marking information to current time, and a travel path recognizer
configured to recognize a travel path on which the vehicle travels
based on the lane marking information. The travel path recognizer
calculates a traveling distance traveled by the vehicle from the
acquisition time of the lane marking information to the current
time based on the vehicle speed of the vehicle behavior, and
determines whether or not the lane marking information is
information within a usable period in which the lane marking
information is usable to recognize the travel path based on a
predetermined lane marking acquirable distance and the traveling
distance. The predetermined lane marking acquirable distance is a
distance in front of the position of the vehicle, and is a distance
in which the lane marking of the lane marking information is
acquirable.
Effects of the Invention
[0007] According to the present invention, the travel path
recognizer calculates a traveling distance traveled by the vehicle
from the acquisition time of the lane marking information to the
current time based on the vehicle speed of the vehicle behavior,
and determines whether or not the lane marking information is
information within a usable period in which the lane marking
information is usable to recognize the travel path based on a
predetermined lane marking acquirable distance and the traveling
distance. The predetermined lane marking acquirable distance is a
distance in front of the position of the vehicle, and is a distance
in which the lane marking of the lane marking information is
acquirable. Consequently, the travel path can be appropriately
recognized.
[0008] These and other objects, features, aspects and advantages of
the present invention will become more apparent from the following
detailed description of the present invention when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a diagram illustrating one example of a
configuration of a drive assist device including a control
unit.
[0010] FIG. 2 is a block diagram illustrating a function of a
travel path recognition apparatus according to a first
embodiment.
[0011] FIG. 3 is a flowchart illustrating operation of the travel
path recognition apparatus according to the first embodiment.
[0012] FIG. 4 is a flowchart illustrating operation of the travel
path recognition apparatus according to the first embodiment.
[0013] FIG. 5 is a diagram illustrating one example of estimation
lane marking information calculation processing of the travel path
recognition apparatus according to the first embodiment.
[0014] FIG. 6 is a diagram illustrating one example of estimation
lane marking information calculation processing of a travel path
recognition apparatus according to a second embodiment.
[0015] FIG. 7 is a diagram illustrating one example of estimation
lane marking information calculation processing of a travel path
recognition apparatus according to a third embodiment.
[0016] FIG. 8 is a block diagram illustrating one example of a
hardware configuration of the travel path recognition
apparatus.
[0017] FIG. 9 is a block diagram illustrating one example of a
hardware configuration of the travel path recognition
apparatus.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0018] A travel path recognition apparatus according to a first
embodiment of the present invention is implemented by a control
unit mounted to a vehicle. FIG. 1 is a configuration diagram
illustrating one example of a configuration of a drive assist
device including a control unit 10 according to the first
embodiment. Note that, in each of the embodiments, the same or
similar parts are denoted by the same reference symbols, and
overlapping description will be omitted as appropriate.
[0019] A steering device 4 steers tires 5 based on behavior of a
steering wheel 2 coupled to the steering device 4. A motor 3 is
coupled to the steering device 4 similarly to a general electric
power steering device. Torque generated by the motor 3 is applied
to the steering device 4 as appropriate. The motor 3 is driven
based on a target electric current output by the control unit
10.
[0020] A wheel speed sensor 6 detects vehicle speed information
concerning a vehicle speed of a vehicle 1. As the vehicle speed
information, for example, a vehicle speed of the vehicle 1, a
traveling distance of the vehicle 1, acceleration of the vehicle 1,
or the like is used. The traveling distance is differentiated with
respect to time to obtain the vehicle speed. The acceleration is
integrated with respect to time to obtain the vehicle speed.
[0021] A yaw rate sensor 7 detects yaw rate information concerning
a yaw rate of the vehicle 1. As the yaw rate information, for
example, a yaw rate of the vehicle 1, a yaw angle of the vehicle 1,
a yaw moment of the vehicle 1, or the like is used. The yaw angle
is differentiated with respect to time to obtain the yaw rate. The
yaw moment is subjected to predetermined calculation to obtain the
yaw rate.
[0022] A camera 8 is installed near a rear-view mirror inside the
vehicle 1, and captures a front-view image of the vehicle 1 through
a windshield of the vehicle 1. The front-view image captured by the
camera 8 is used to detect lane marking information to be described
later in detail.
[0023] A millimeter wave radar 9 measures an inter-vehicle distance
between a preceding vehicle, which is another vehicle in front of
the vehicle 1, and the vehicle 1.
[0024] The control unit 10 is directly or indirectly connected to
the motor 3, the wheel speed sensor 6, the yaw rate sensor 7, the
camera 8, and the millimeter wave radar 9. A signal from each
sensor, the front-view image from the camera 8, and the
inter-vehicle distance from the millimeter wave radar 9 are input
to the control unit 10. The control unit 10 determines a target
electric current, which is a drive signal of the motor 3, based on
these pieces of input information, and outputs the target electric
current to the motor 3. Note that the control unit 10 may include a
control function of a general electric power steering device.
[0025] FIG. 2 is a block diagram illustrating a function of the
travel path recognition apparatus implemented by the control unit
10. A travel assist apparatus of FIG. 2 includes a vehicle behavior
detector 21, a lane marking detector 22 that detects lane marking
information, a travel path recognizer 23, and an inter-vehicle
distance detector 24.
[0026] The vehicle behavior detector 21 serving as a vehicle
behavior acquisition unit includes a vehicle speed detector 21a and
a yaw rate detector 21b. The vehicle speed detector 21a detects a
vehicle speed of the vehicle 1 on certain occasions from the time
when the lane marking detector 22 detects lane marking information
to the current time based on the vehicle speed information detected
by the wheel speed sensor 6. The yaw rate detector 21b detects a
yaw rate of the vehicle 1 on certain occasions from the time when
the lane marking detector 22 detects lane marking information to
the current time based on the yaw rate information detected by the
yaw rate sensor 7.
[0027] The vehicle behavior detector 21 configured as described
above detects vehicle behavior concerning the vehicle speed and the
yaw rate of the vehicle 1 from the detection time of the lane
marking information to the current time. The vehicle behavior
detector 21 outputs the detected vehicle behavior to the travel
path recognizer 23.
[0028] The inter-vehicle distance detector 24 serving as an
inter-vehicle distance acquisition unit acquires a signal of the
inter-vehicle distance between the preceding vehicle and the
vehicle 1 detected by the millimeter wave radar 9, and outputs the
inter-vehicle distance to the travel path recognizer 23. Note that
a configuration of detecting the inter-vehicle distance between the
preceding vehicle and the vehicle 1 based on the front-view image
captured by the camera 8 may be adopted. In this case, the
millimeter wave radar 9 can be omitted, and can thus achieve cost
reduction.
[0029] The lane marking detector 22 serving as a lane marking
acquisition unit detects lane marking information based on data of
the front-view image captured by the camera 8, and outputs the
detected lane marking information to the travel path recognizer 23
on a 0.1-msec cycle, for example. The lane marking information is
information concerning a position and a shape of the lane marking
in front of the vehicle 1 with respect to a position of the vehicle
1 at the time of capturing the image. The lane marking information
includes, for example, a vehicle-lane marking distance, a vehicle
angle, curvature of the lane marking, and a curvature change rate
of the lane marking. The vehicle-lane marking distance is a
distance between the vehicle 1 and a portion of the lane marking on
a side of the vehicle. The vehicle angle is inclination of a
traveling direction of the vehicle 1 with respect to the portion of
the lane marking.
[0030] Here, a detection method of the lane marking information
will be described. From the front-view image captured by the camera
8, the lane marking detector 22 extracts lane markings, such as
white lines, located on both the right and left sides of a road in
the front-view image by using a known method. Then, the lane
marking detector 22 calculates curvature and a curvature change
rate of the obtained lane markings. The following description is
based on an assumption that the calculated curvature change rate is
constant within the captured area. In this case, based on the
curvature at the image-capture (detection) position and the
curvature change rate being constant within the captured area, the
lane marking detector 22 calculates the above-mentioned curvature
of a portion of the captured lane marking in front of the vehicle 1
with respect to the position of the vehicle 1 at the image-capture
time point. Further, the lane marking detector 22 estimates a lane
marking extended to the position of the vehicle 1 with an
extrapolation method by using a known method. Then, as the
above-mentioned vehicle-lane marking distance, the lane marking
detector 22 calculates a distance from the position of the vehicle
1 at the image-capture time point to the estimated lane marking.
Further, as the above-mentioned vehicle angle, the lane marking
detector 22 calculates inclination of the traveling direction of
the vehicle 1 at the image-capture time point with respect to the
estimated lane marking. Note that the position of the vehicle 1
when the lane marking information is detected may be hereinafter
referred to as a "detection position".
[0031] The detail of the travel path recognizer 23 will be
described later with reference to a flowchart. Thus, a main
configuration of the travel path recognizer 23 will now be
described.
[0032] The travel path recognizer 23 recognizes a travel path on
which the vehicle 1 travels based on the lane marking information
detected by the lane marking detector 22. Further, the travel path
recognizer 23 stores the lane marking information detected by the
lane marking detector 22. The lane marking information stored by
the travel path recognizer 23 may be hereinafter referred to as
"stored lane marking information."
[0033] The travel path recognizer 23 does not only store the lane
marking information, but also stores vehicle behavior and a lane
marking detectable distance that correspond to the lane marking
information. Here, the lane marking detectable distance refers to a
distance in front of the detection position of the vehicle 1, and
to a predetermined distance in which the lane marking of the lane
marking information can be detected. Note that the lane marking
detectable distance may be referred to as a lane marking acquirable
distance. In the first embodiment, the travel path recognizer 23
controls the lane marking detectable distance based on the
inter-vehicle distance detected by the inter-vehicle distance
detector 24.
[0034] When the lane marking information is detected by the lane
marking detector 22, the travel path recognizer 23 uses the
detected lane marking information to recognize the travel path, and
outputs the detected lane marking information to the outside.
[0035] On the other hand, when the lane marking information is not
detected by the lane marking detector 22, the travel path
recognizer 23 uses the stored lane marking information to recognize
the travel path. At this time, the travel path recognizer 23
determines whether or not the stored lane marking information is
information within a usable period in which the stored lane marking
information can be used to recognize the travel path.
[0036] Specifically, the travel path recognizer 23 calculates a
post-detection traveling distance, which is a traveling distance
traveled by the vehicle 1 from the detection time of the lane
marking information to the current time, based on the vehicle speed
of the vehicle behavior detected by the vehicle behavior detector
21. Then, the travel path recognizer 23 determines whether or not
the stored lane marking information is information within the
usable period in which the stored lane marking information can be
used to recognize the travel path based on the above-mentioned
post-detection traveling distance and the above-mentioned lane
marking detectable distance.
[0037] When the travel path recognizer 23 determines that the
stored lane marking information is information within the usable
period, the travel path recognizer 23 corrects the stored lane
marking information within the usable period into current-position
lane marking information based on the vehicle behavior, and uses
the current-position lane marking information to recognize the
travel path. Note that the current-position lane marking
information is information concerning a position and a shape of the
lane marking with respect to the current position of the vehicle 1.
On the other hand, when the travel path recognizer 23 determines
that the stored lane marking information is not information within
the usable period, the travel path recognizer 23 discards the
stored lane marking information, i.e., erases the stored lane
marking information from memory.
[0038] <Operation>
[0039] FIG. 3 is a flowchart illustrating operation of the travel
path recognition apparatus according to the first embodiment. The
operation of FIG. 3 is performed on a certain cycle, for example,
on a 0.01-second cycle.
[0040] First, in Step S1, the lane marking detector 22 performs
lane marking detection processing to detect lane marking
information. The lane marking detector 22 detects lane marking
information including the above-mentioned vehicle-lane marking
distance, vehicle angle, curvature, and curvature change rate by
using the above-mentioned detection method or the like. Note that,
although not illustrated, vehicle behavior is also detected
depending on the detection of the lane marking information.
[0041] In Step S2, the travel path recognizer 23 performs travel
path recognition processing to estimate the above-mentioned
current-position lane marking information as estimation lane
marking information depending on a condition. Consequently, even
when the lane marking information cannot be detected by the lane
marking detector 22 due to deterioration in detectability or the
like, the travel path recognizer 23 outputs appropriate estimation
lane marking information and recognizes the travel path on which
the vehicle 1 travels based on the estimation lane marking
information. In the first embodiment, the control unit 10 (FIG. 2)
implementing the travel path recognition apparatus controls an
electric current of the motor 3 based on the travel path recognized
by the travel path recognizer 23 to perform known steering angle
control. This can optimize a lane keep assist function, which
maintains traveling of the vehicle 1 along a portion, such as a
center portion between traffic lanes, for example.
[0042] FIG. 4 is a flowchart illustrating the detail of the travel
path recognition processing in Step S2 of FIG. 3.
[0043] First, in Step S11, the travel path recognizer 23 performs
vehicle behavior integration that integrates vehicle behavior
corresponding to the stored lane marking information. The travel
path recognizer 23 integrates the vehicle behavior from the time of
detecting the lane marking to the current time for every cycle to
acquire a position and a traveling direction of the vehicle 1 that
has changed from the detection time to the current time. These
pieces of information are used to convert a coordinate system of
intermediate lane marking information to be described later, for
example.
[0044] In Step S12, the travel path recognizer 23 determines
whether or not new lane marking information, which is the latest
lane marking information obtained by the lane marking detector 22,
has been detected. If it is determined that the new lane marking
information has been detected, processing proceeds to Step S13. If
it is determined that the new lane marking information has not been
detected, processing proceeds to Step S15.
[0045] In Step S13, the travel path recognizer 23 acquires the new
lane marking information and the position of the vehicle 1 at the
detection time of the new lane marking information from the lane
marking detector 22 etc., and stores the new lane marking
information and the position.
[0046] Note that, regarding the position of the vehicle 1 at the
detection time, influence caused by a time difference between a
first time point and a second time point may not be tolerated in
some cases. The first time point is a time point when the lane
marking detector 22 detects the lane marking. The second time point
is a time point when the travel path recognizer 23 acquires the
lane marking information. Examples of the cause of such a time
difference include a period of time required for the calculation
when the front-view image captured by the camera 8 is processed to
obtain the lane marking information, a communication delay caused
by communication through a communication line such as a controller
area network (CAN), etc. For example, when the degree of the time
different is such a degree that may be tolerated (e.g.,
approximately 0.01 sec), the above-mentioned first time point and
the above-mentioned second time point may be regarded as an
identical time point, and thus a deviation of both of a traveling
distance and a vehicle rotation angle caused by the time difference
may be 0. On the other hand, for example, when the degree of the
time difference is such a degree that may not be tolerated (e.g.,
approximately 0.1 sec), the vehicle 1 travels several meters during
the time period. In such a case, the travel path recognizer 23 may
use the acquired position of the vehicle 1 as a position of the
vehicle 1 detected 0.1 sec earlier than the acquisition time point.
The position of the vehicle 1 earlier than 0.1 sec can be obtained
by integrating the vehicle behavior during the 0.1 sec, similarly
to Step S11 described above.
[0047] In Step S14, the travel path recognizer 23 estimates an area
in which the lane marking in front of the vehicle 1 can be detected
based on the inter-vehicle distance detected by the inter-vehicle
distance detector 25 to control the above-mentioned lane marking
detectable distance. The control of the lane marking detectable
distance includes setting, changing, and storing the lane marking
detectable distance, for example.
[0048] Here, when a preceding vehicle does not exist and the
inter-vehicle distance is sufficiently long, there is no
obstruction to the area in which the lane marking detector 22 can
detect the lane marking in front. Therefore, as the lane marking
detectable distance, the travel path recognizer 23 sets a maximum
distance (e.g., 100 m), in which the lane marking in front of the
vehicle 1 can be detected depending on capacity of the camera 8 or
the like. At the same time, regarding the lane marking located away
from the vehicle 1 by the maximum distance or more, it can be said
that the stored lane marking information of the lane marking is not
appropriate. Therefore, when the post-detection traveling distance,
which is a distance traveled by the vehicle 1 from the detection
time of the stored lane marking information, exceeds the lane
marking detectable distance, it can be said that accuracy of the
stored lane marking information is lowered. Accordingly, as will be
described later, when it is determined that the new lane marking
information has not been detected and the processing proceeds from
Step S12 to Step S15, and the post-detection traveling distance
exceeds the lane marking detectable distance, the travel path
recognizer 23 erases the stored lane marking information from the
memory in Step S9.
[0049] When a preceding vehicle exists and the inter-vehicle
distance is short, it is assumed that the area in which the lane
marking detector 22 can detect the lane marking in front of the
vehicle 1 is obstructed by the preceding vehicle and is narrowed.
In the first embodiment, information detected by the inter-vehicle
distance detector 24 is only an inter-vehicle distance, and a size
of the preceding vehicle and a horizontal position in the traffic
lane cannot be detected. Accordingly, when the inter-vehicle
distance is short, the travel path recognizer 23 sets the
inter-vehicle distance between the vehicle and the preceding
vehicle as the lane marking detectable distance.
[0050] Note that, if the shape of the preceding vehicle and the
horizontal position in the traffic lane can be obtained in a
configuration of detecting the inter-vehicle distance by using the
camera 8 instead of using the millimeter wave radar 9, the travel
path recognizer 23 may use those pieces of information to control
the lane marking detectable distance. For example, when the
preceding vehicle is a small-sized vehicle, the lane marking
further in front of the preceding vehicle may be detected in some
cases. Thus, it is sufficient to calculate a portion that is not
hidden by the preceding vehicle to estimate the area in which the
lane marking in front can be detected. In this case, the travel
path recognizer 23 may set a distance equal to or greater than the
inter-vehicle distance between the vehicle 1 and the preceding
vehicle as the lane marking detectable distance. After Step S14,
the processing proceeds to Step S18.
[0051] If the processing proceeds from Step S12 to Step S15, the
travel path recognizer 23 compares the post-detection traveling
distance obtained based on the vehicle behavior updated in Step S11
and stored in Step S13 to the lane marking detectable distance
controlled in Step S14, and determines whether or not the lane
marking information is information within the usable period.
[0052] Here, when the post-detection traveling distance is equal to
or less than the lane marking detectable distance, the travel path
recognizer 23 determines that the lane marking information stored
in Step S13 is information within the usable period, and the
processing proceeds to Step S16. On the other hand, when the
post-detection traveling distance exceeds the lane marking
detectable distance, the travel path recognizer 23 determines that
the lane marking information stored in Step S13 is not information
within the usable period, and the processing proceeds to Step
S19.
[0053] In Steps S16 and S17, the travel path recognizer 23
estimates the current-position lane marking information based on
the stored lane marking information within the usable period as the
estimation lane marking information. The operation of Steps S16 and
S17 will be described below with reference to FIG. 5 illustrating
one example of estimation of the estimation lane marking
information.
[0054] First, in Step S16, the travel path recognizer 23 reads out
lane marking information from the stored lane marking information,
and calculates intermediate lane marking information based on a
vehicle-lane marking distance k0, a vehicle angle k1, curvature k2,
and a curvature change rate k3 included in the lane marking
information.
[0055] Note that the intermediate lane marking information is
information in the middle of conversion from lane marking
information to current-position lane marking information. Here, the
intermediate lane marking information is information concerning a
position and a shape of a lane marking in a detection-position
coordinate system of a case where the vehicle 1 travels from a
detection position DP (FIG. 5) that is a position of the vehicle 1
when the lane marking information is detected to the current
position CP (FIG. 5).
[0056] The detection-position coordinate system is a coordinate
system with respect to the detection position DP. In the example of
FIG. 5, as the detection-position coordinate system, an orthogonal
coordinate system in which a front-and-back direction and a
right-and-left direction of the vehicle 1 at the detection position
DP are respectively represented by an x direction and a y direction
is used. Since the intermediate lane marking information is
information concerning the position and the shape of the lane
marking as described above, the intermediate lane marking
information includes a vehicle-lane marking distance, a vehicle
angle, curvature, and a curvature change rate, similarly to the
lane marking information.
[0057] Next, operation that the travel path recognizer 23
calculates the intermediate lane marking information will be
described.
[0058] A vehicle-lane marking distance k0(L), a vehicle angle
k1(L), and curvature k2(L) of the lane marking in the
detection-position coordinate system when the vehicle 1 travels a
distance L [mJ] from the detection position DP may be calculated by
using the following formula (1) including k0 to k2 of the lane
marking information. Note that a curvature change rate k3(L) is
constant as described above, and is equal to k3.
[ Formula 1 ] k 0 ( L ) = k 0 + k 1 .times. L + 1 2 .times. k 2
.times. L 2 + 1 6 .times. k 3 .times. L 3 k 1 ( L ) = k 1 + k 2
.times. L + 1 2 .times. k 3 .times. L 2 k 2 ( L ) = k 2 + k 3
.times. L } ( 1 ) ##EQU00001##
[0059] The travel path recognizer 23 calculates a distance from the
detection position DP to the current position CP based on an
integration value of the vehicle behavior acquired and updated in
Steps S11 and S13. Then, the travel path recognizer 23 substitutes
the distance for L of the formula (1) above to calculate a
vehicle-lane marking distance, a vehicle angle, and curvature of
the intermediate lane marking information.
[0060] In a strict sense, a deviation corresponding to an
inclination amount of the vehicle 1 at the current position CP is
generated. However, it is assumed that the vehicle 1 travels at a
relatively high speed during operation of the lane keep assist, and
thus a deviation of the inclination of the vehicle 1 is hardly
generated in actuality. Therefore, in order to calculate the
intermediate lane marking information, it is sufficient that a
vertical movement amount (dx in FIG. 5), which is a movement amount
in the x direction from the detection position DP to the current
position CP, be substituted for L. In contrast, when the
above-mentioned deviation may not be tolerated due to low-speed
traveling and a relatively large steering angle, such as in a case
of following a preceding vehicle during traffic congestion, the
calculation may be performed in consideration of an inclination
amount of the vehicle at the current position CP.
[0061] Next, calculation of the vertical movement amount dx based
on the integration value of the vehicle behavior will be described.
Note that, in addition to the above-mentioned vertical movement
amount dx, examples of the values that can be calculated based on
an integration value of the vehicle behavior include a horizontal
movement amount dy, which is a movement amount in the y direction
from the detection position DP to the current position CP, and a
vehicle angle change .theta., which is an angle formed between the
x direction of the detection position DP and the x direction of the
current position CP. Such values can be calculated as below.
[0062] First, the vehicle angle change .theta. can be calculated by
integrating the yaw rate from the detection time to the current
time. The vertical movement amount dx and the horizontal movement
amount dy can be calculated by integrating the vehicle speed from
the detection time to the current time, and then separating a
traveling distance (Svsp) obtained by the integration into an
x-direction component and a y-direction component by using the
vehicle angle change 9. In a strict sense, an error is generated
due to erratic driving or the like also in the vehicle movement
distance such as the vertical movement amount dx and the horizontal
movement amount dy. However, similarly to the above, it is assumed
that the vehicle 1 travels at a relatively high speed, and thus it
can be said that the error and influence of the error are trivial.
Note that, if .theta. is small, a calculation load may be reduced
as in the following formula (2) by carrying out approximation as
sin(.theta.).apprxeq..theta. and
cos(.theta.).apprxeq.1-.theta..sup.2/2.
[ Formula 2 ] dx = Svsp .times. cos ( .theta. ) .apprxeq. Svsp
.times. ( 1 - .theta. 2 2 ) dy = Svsp .times. sin ( .theta. )
.apprxeq. Svsp .times. .theta. } ( 2 ) ##EQU00002##
[0063] In view of the above, the travel path recognizer 23 is
configured to calculate the vertical movement amount dx based on
the integration value of the vehicle behavior acquired and updated
in Steps S11 and S13 and substitute the vertical movement amount dx
for L of the formula (1) above to calculate the intermediate lane
marking information.
[0064] Through Step S16 (FIG. 4) described in the above, the travel
path recognizer 23 acquires the intermediate lane marking
information.
[0065] After Step S16, in Step S17, the travel path recognizer 23
converts the coordinate system of the intermediate lane marking
information obtained in Step S16 from the detection-position
coordinate system with respect to the detection position DP (FIG.
5) to a current-position coordinate system with respect to the
current position CP (FIG. 5) to correct the intermediate lane
marking information into current-position lane marking information.
This enables use of values corresponding to the current position of
the vehicle 1 in control, for example.
[0066] Note that the current-position lane marking information is
information concerning the position and the shape of the lane
marking with respect to the current-position coordinate system. In
the example of FIG. 5, as the current-position coordinate system,
an orthogonal coordinate system in which a front-and-back direction
and a right-and-left direction of the vehicle 1 at the current
position CP are respectively represented by an x' direction and a
y' direction is used. Since the current-position lane marking
information is information concerning the position and the shape of
the lane marking as described above, the current-position lane
marking information includes a vehicle-lane marking distance, a
vehicle angle, curvature, and a curvature change rate, similarly to
the lane marking information.
[0067] Next, operation that the travel path recognizer 23
calculates the current-position lane marking information will be
described.
[0068] First, regarding the vehicle-lane marking distance of the
current-position lane marking information, it is sufficient that
k0(dx) be converted from the detection-position coordinate system
to the current-position coordinate system by using a known method
of converting coordinates. For example, with respect to k0(dx), an
amount corresponding to a movement distance (dx, dy) from the
detection position DP to the current position CP is deviated, and
then an amount corresponding to a vehicle angle change (.theta.) is
rotated. Consequently, a vehicle-lane marking distance k0' of the
current-position lane marking information can be obtained. Note
that the position of the vehicle 1 in the x direction in the
detection-position coordinate system of k0' is dx, and the position
of the vehicle 1 in the x' direction in the current-position
coordinate system is 0. From the description above, the
vehicle-lane marking distance k0' of the current-position lane
marking information is expressed as in the following formula (3).
Accordingly, the travel path recognizer 23 applies k0(dx) of the
intermediate lane marking information and dy and .theta. calculated
based on the vehicle behavior to the following formula (3) to
calculate a vehicle-lane marking distance k0' of the
current-position lane marking information.
[Formula 3]
k0'=(k0(dx)-dy).times.cos(.theta.) (3)
[0069] The vehicle angle of the current-position lane marking
information is inclination between the vehicle inclination and the
lane marking at the detection time in the detection-position
coordinate system, and thus needs to be converted to the current
vehicle inclination. A change amount of the vehicle inclination
from the detection time to the current time is .theta., and
therefore the vehicle angle of the current-position lane marking
information is expressed as in the following formula (4).
Accordingly, the travel path recognizer 23 applies k1(dx) of the
intermediate lane marking information and .theta. calculated based
on the vehicle behavior to the following formula (4) to calculate a
vehicle angle k1' of the current-position lane marking
information.
[Formula 4]
k1'=k1(dx)-.theta. (4)
[0070] The curvature of the lane marking of the current-position
lane marking information is not influenced by inclination of the
vehicle 1, and therefore the curvature of the lane marking of the
intermediate lane marking information can be used as it is. The
curvature of the current-position lane marking information is
expressed as in the following formula (5). Accordingly, the travel
path recognizer 23 applies k2(dx) of the intermediate lane marking
information to the following formula (5) to calculate curvature of
the current-position lane marking information.
[Formula 5]
k2'=k2(dx) (5)
[0071] Through Step S17 described in the above, the travel path
recognizer 23 acquires the current-position lane marking
information and uses the current-position lane marking information
as the estimation lane marking information.
[0072] If the processing proceeds from Step S14 to Step S18, the
travel path recognizer 23 outputs the lane marking information
stored in Step S13, and the processing of FIG. 4 ends. If the
processing proceeds from Step S17 to Step S18, the travel path
recognizer 23 outputs the current-position lane marking information
acquired in Step S17, and the processing of FIG. 4 ends.
[0073] If the processing proceeds from Step S15 to Step S19, the
travel path recognizer 23 determines that accuracy of the lane
marking information stored in Step S13 is lowered, and erases the
lane marking information from the memory. After that, the
processing of FIG. 4 ends.
Gist of First Embodiment
[0074] According to the travel path recognition apparatus of the
first embodiment as described above, the travel path recognizer 23
determines whether or not the lane marking information is
information within the usable period in which the lane marking
information can be used to recognize the travel path based on the
post-detection traveling distance and the lane marking detectable
distance. Therefore, the travel path can be appropriately
recognized.
[0075] Further, in the first embodiment, the travel path recognizer
23 controls the lane marking detectable distance based on the
inter-vehicle distance detected by the inter-vehicle distance
detector 24. Consequently, an appropriate lane marking detectable
distance can be used, and therefore the travel path can be
appropriately recognized.
[0076] Further, in the first embodiment, the travel path recognizer
23 uses the lane marking information corrected based on the vehicle
behavior to estimate the current-position lane marking information.
Therefore, accuracy of the estimation can be enhanced.
Second Embodiment
[0077] The travel path recognition apparatus according to the first
embodiment is configured such that the lane marking detectable
distance is controlled based on the inter-vehicle distance detected
by the inter-vehicle distance detector 24. However, the
configuration is not limited to the above. The lane marking
detectable distance may be controlled based on a road shape as in a
travel path recognition apparatus according to a second embodiment
of the present invention described below.
[0078] Note that a block configuration and operation of the travel
path recognition apparatus according to the second embodiment are
substantially the same as the block configuration and the operation
of the travel path recognition apparatus according to the first
embodiment, except for Step S14 (FIG. 4). Accordingly, Step S14
will be mainly described below.
[0079] In Step S14 according to the second embodiment, the travel
path recognizer 23 controls the lane marking detectable distance
based on the curvature of the lane marking included in the lane
marking information acquired in Step S13, instead of the
inter-vehicle distance detected by the inter-vehicle distance
detector 24.
[0080] FIG. 6 is a diagram illustrating one example of operation of
controlling the lane marking detectable distance based on the
curvature of the lane marking.
[0081] Note that it is assumed that the camera 8 (FIG. 1) used
herein generates distortion or the like at a boundary portion of a
viewing angle, i.e., at an image peripheral portion. Further, it is
assumed that the image peripheral portion refers to a portion
outside of .+-.30 degrees on the right and left sides (60 degrees
on both the sides). In this case, the travel path recognition
apparatus according to the second embodiment can detect a lane
marking L1 within an area of a circular sector (FIG. 6 illustrates
the right half of the circular sector).
[0082] It is assumed that the vehicle 1 travels along a tangential
direction of the lane marking L1 of a radius of curvature R. When
an intersection point P1 between the lane marking L1 and the
detection area (on the right side) is located at a position in
front of the vehicle 1 by a distance Lp, the distance Lp may be
calculated based on the following formula (6) employing the formula
of the Pythagorean theorem illustrated in FIG. 6.
[Formula 6]
Lp=R (6)
[0083] The lane marking L1 farther than the intersection point P1
cannot be appropriately detected, and thus the distance Lp can be
used as the lane marking detectable distance. Note that Radius of
Curvature R=1/(Curvature of Lane Marking) holds. In view of the
description above, the travel path recognizer 23 applies the
curvature of the lane marking included in the lane marking
information acquired in Step S13 to the formula of Lane Marking
Detectable Distance=1/(Curvature of Lane Marking) to control the
lane marking detectable distance.
Gist of Second Embodiment
[0084] According to the travel path recognition apparatus of the
second embodiment as described above, the travel path recognizer 23
controls the lane marking detectable distance based on the
curvature of the lane marking. Consequently, an appropriate lane
marking detectable distance can be used, and therefore the travel
path can be appropriately recognized. Further, in this case, the
millimeter wave radar 9 of FIG. 1, the inter-vehicle distance
detector 24 of FIG. 2, and the control processing of the lane
marking detectable distance based on the inter-vehicle distance of
Step S14 of FIG. 4 are unnecessary.
[0085] Note that, if necessary, the travel path recognizer 23 may
control the lane marking detectable distance based on the
inter-vehicle distance detected by the inter-vehicle distance
detector 24 and the curvature of the lane marking included in the
lane marking information. For example, the travel path recognizer
23 may use a shorter distance of the distance obtained based on the
inter-vehicle distance and the distance obtained based on the
curvature of the lane marking as the lane marking detectable
distance.
Third Embodiment
[0086] The travel path recognition apparatus according to the
second embodiment is configured such that the lane marking
detectable distance is controlled based on the curvature of the
lane marking. However, the configuration is not limited to the
above. The lane marking detectable distance may be controlled also
in consideration of the vehicle angle included in the lane marking
information in addition to the curvature of the lane marking as in
a travel path recognition apparatus according to a third embodiment
of the present invention described below.
[0087] For example, in general, the vehicle speed tends to be
lower, the curvature larger (a curve sharper), and the vehicle
angle with respect to the lane marking larger in a case of
preceding-vehicle following control during traffic congestion or
the like than in a case of using the lane keep assist function in
an expressway. Accordingly, in the third embodiment, the travel
path recognizer 23 estimates an area in which the lane marking can
be detected also in consideration of the lane marking and the
vehicle behavior to control the lane marking detectable
distance.
[0088] Note that a block configuration and operation of the travel
path recognition apparatus according to the third embodiment are
substantially the same as the block configuration and the operation
of the travel path recognition apparatus according to the first
embodiment, except for Step S14 (FIG. 4). Accordingly, Step S14
will be mainly described below.
[0089] In Step S14 according to the third embodiment, the travel
path recognizer 23 controls the lane marking detectable distance
based on the curvature of the lane marking included in the lane
marking information acquired in Step S13 and the vehicle angle,
instead of the inter-vehicle distance detected by the inter-vehicle
distance detector 24.
[0090] FIG. 7 is a diagram illustrating one example of operation of
controlling the lane marking detectable distance based on the
curvature of the lane marking and the vehicle angle.
[0091] FIG. 7 illustrates a state in which the vehicle angle has
been inclined by .theta. degrees in a direction that the lane
marking L1 and the detection area separate away from each other in
the state of FIG. 6. In this case, if the viewing angle is 30
degrees, an angle formed between a radius direction of the lane
marking L1 of the vehicle 1 and a direction from the vehicle 1
toward the intersection point P1 is (60+.theta.) degrees.
[0092] Also in the third embodiment, similarly to the second
embodiment, it is assumed that the vehicle 1 travels along the
tangential direction of the lane marking L of the radius of
curvature R. When the intersection point P1 between the lane
marking L1 and the detection area (on the right side) is located at
a position in front of the vehicle 1 by the distance Lp, the
distance Lp may be calculated based on the following formula (7)
employing the formula of the Pythagorean theorem illustrated in
FIG. 7.
[Formula 7]
Lp=2.times.cos(60+.theta.).times.R (7)
[0093] Similarly to the second embodiment, the travel path
recognizer 23 applies the curvature of the lane marking included in
the lane marking information acquired in Step S13 and the vehicle
angle to the formula of Lane Marking Detectable
Distance=2.times.cos(60+Vehicle Angle)/(Curvature of Lane Marking)
to control the lane marking detectable distance.
Gist of Third Embodiment
[0094] According to the travel path recognition apparatus of the
third embodiment as described above, the travel path recognizer 23
controls the lane marking detectable distance based on the
curvature of the lane marking and the vehicle angle. Consequently,
an appropriate lane marking detectable distance can be used, and
therefore the travel path can be appropriately recognized. Further,
in this case, the millimeter wave radar 9 of FIG. 1, the
inter-vehicle distance detector 24 of FIG. 2, and the control
processing of the lane marking detectable distance based on the
inter-vehicle distance of Step S14 of FIG. 4 are unnecessary.
[0095] Note that, if necessary, the travel path recognizer 23 may
control the lane marking detectable distance based on the
inter-vehicle distance detected by the inter-vehicle distance
detector 24 and the curvature of the lane marking included in the
lane marking information. For example, the travel path recognizer
23 may use a shorter distance of the distance obtained based on the
inter-vehicle distance and the distance obtained based on the
curvature of the lane marking and the vehicle angle as the lane
marking detectable distance.
[0096] <Modification>
[0097] The description above describes a device using results of
recognition of a travel path in the lane keep assist, but this is
not restrictive. The results of recognition of a travel path may be
used in a traffic-lane deviation alarm device, an automated driving
device, or the like. The technology described in the embodiments
may be applied in each of the devices when lane marking information
and a travel path are used.
[0098] <Other Modification>
[0099] The lane marking acquisition unit, the vehicle behavior
acquisition unit, and the travel path recognizer of the travel path
recognition apparatus are hereinafter referred to as "lane marking
acquisition unit etc." The lane marking acquisition unit etc. are
implemented by a processing circuit 81 of FIG. 8 corresponding to
the control unit 10 of FIG. 1. Specifically, the processing circuit
81 includes a lane marking acquisition unit that acquires lane
marking information, a vehicle behavior acquisition unit that
acquires vehicle behavior concerning a vehicle speed of the vehicle
1 from acquisition time of the lane marking information to current
time, and a travel path recognizer that recognizes a travel path on
which the vehicle 1 travels based on the lane marking information.
The processing circuit 81 may use dedicated hardware, or may use a
processor to execute a program stored in memory. Examples of the
processor include a central processing unit, a processing unit, an
arithmetic unit, a microprocessor, a microcomputer, a digital
signal processor (DSP), etc.
[0100] If the processing circuit 81 is dedicated hardware, examples
of the processing circuit 81 include a single circuit, a composite
circuit, a programmed processor, a processor for parallel
programming, an application specific integrated circuit (ASIC), a
field programmable gate array (FPGA), or a combination of these.
The function of each part of the lane marking acquisition unit etc.
may be implemented by a circuit in which processing circuits are
distributed, or the function of each part may be collectively
implemented by one processing circuit.
[0101] If the processing circuit 81 is a processor, the functions
of the lane marking acquisition unit etc. are implemented by a
combination with software etc. Note that examples of the software
etc. include software, firmware, or software and firmware. Software
etc. are described as a program, and are stored in memory. As
illustrated in FIG. 9, a processor 83 used in the processing
circuit 81 reads out and executes a program stored in memory 84 to
implement a function of each part that processes a signal input and
output between the processor 83 and an external device, such as the
wheel speed sensor 6, the yaw rate sensor 7, the camera 8, and the
motor 3 of FIG. 1, via an input-output control interface (I/F) 82.
Specifically, the travel path recognition apparatus includes the
memory 84 for storing the program that eventually executes a step
of acquiring lane marking information, a step of acquiring vehicle
behavior concerning a vehicle speed of the vehicle 1 from
acquisition time of the lane marking information to current time,
and a step of recognizing a travel path on which the vehicle 1
travels based on the lane marking information, when the program is
executed by the processing circuit 81. In other words, it can be
said that the program makes a computer execute a procedure and a
method of the lane marking acquisition unit etc. Here, examples of
the memory 84 may include a non-volatile or volatile semiconductor
memory, such as random access memory (RAM), read only memory (ROM),
flash memory, erasable programmable read only memory (EPROM), and
electrically erasable programmable read only memory (EEPROM), a
hard disk drive (HDD), a magnetic disk, a flexible disk, an optical
disc, a compact disc, a MiniDisc, a digital versatile disc (DVD), a
drive device therefor, and any storage medium that may be used
ahead.
[0102] In the above, a configuration in which each function of the
lane marking acquisition unit etc. is implemented by any one of
hardware and software etc. is described. However, the configuration
is not limited to the above, and a configuration in which a part of
the lane marking acquisition unit etc. is implemented by dedicated
hardware and another part is implemented by software etc. may be
adopted. For example, the function of the lane marking acquisition
unit and the vehicle behavior acquisition unit may be implemented
by a processing circuit as dedicated hardware, such as a receiver.
The function of other parts may be implemented by the processing
circuit 81 as the processor 83 reading out and executing the
program stored in the memory 84.
[0103] In this manner, the processing circuit 81 may implement the
above-mentioned each function by hardware, software etc., or a
combination of these.
[0104] Further, the travel path recognition apparatus described
above may also be used in a travel path recognition system
constructed as a system achieved by appropriately combining a
navigation device such as a portable navigation device (PND), a
communication terminal including a portable terminal such as a
mobile phone, a smartphone, and a tablet, a function of an
application installed in these devices, and a server. In this case,
each function or each component of the travel path recognition
apparatus described above may be distributed in each device that
constructs the above-mentioned system, or may be centralized in any
of the devices.
[0105] Note that, in the present invention, each of the embodiments
and each of the modifications may be freely combined, and each of
the embodiments and each of the modifications may be modified or
omitted as appropriate within the scope of the present
invention.
[0106] While the invention has been shown and described in detail,
the foregoing description is in all aspects illustrative and not
restrictive. It is therefore understood that numerous unillustrated
modifications can be devised without departing from the scope of
the invention.
EXPLANATION OF REFERENCE SIGNS
[0107] 1 vehicle, 21 vehicle behavior detector, 22 lane marking
detector, 23 travel path recognizer, 24 inter-vehicle distance
detector
* * * * *